Besides the 2-hour Sepilok Water Hole jungle trekking, you may try other paths, but you need to register at SORC first. If you are a hardcore jungle trekker, you may try the 5 KM Mangrove Forest trail, which takes 4 hours one way. For this trail, you must contact the Forestry Department for a permit (they will fax it to SORC) and register at SORC. For my case, they faxed the permit to SORC in less than an hour upon request. It will be a full day tour and I am too poor to hire a guide, so I did not go.